The present invention relates to a transmission mechanism for vehicles, for example a transmission mechanism suitable to tractors.
Such a transmission mechanism includes main clutch means adapted to transmit the power of an engine, a primary propeller shaft for primary transmission adapted to be intermittently rotated upon receipt of the engine power by the operation of the main clutch means, a first transmission system for the travelling system adapted to transmit the transmission power of the primary propeller shaft, and a reduction gearing for interlocking a secondary propeller shaft with a second transmission system for transmitting the transmission power thereof.
When the primary clutch and the secondary clutch are turned ON, the transmission power through the primary clutch is transmitted to the first transmission system for the travelling system through the primary propeller shaft, thereby to be further transmitted to the wheels, and the transmission power through the secondary clutch is transmitted to the second transmission system through the secondary propeller shaft, thereby to drive a working machine. If overload is applied to the wheels in such arrangements, the number of rotations of the engine is extremely dropped so that no efficient working is expected, and in the worst case, the engine is stopped. Such inconveniences also take place when the propelling resistance of the wheels is increased by overload applied to the working machine, for example a cultivator, or when the number of rotations of the secondary propeller shaft which drives such cultivator is decreased and the number of rotations of the engine is directly dropped.
It has therefore been desired to construct the transmission mechanism so that efficient working be possible even though overload is applied to the wheels.